The Senate health care reform bill remains on precarious ground after Republican leaders released the revised text of the legislation Thursday, dangling just one “no” vote from defeat as Majority Leader Mitch McConnell, R-KY., scrambles to win over the few remaining undecided moderates.

The new bill includes a provision proposed by Sen. Ted Cruz, R-Texas, that would allow insurance companies to sell more basic and affordable plans on the individual markets as long as they offer at least one that conforms to the requirements of the Affordable Care Act, also known as Obamacare.

The new text boosts funding for opioid addiction treatment, a significant issue for swing state senators like Rob Portman, R-Ohio, and Shelley Moore Capito, R-W.V. It also adds more money for the State Stability and Innovation Program aimed at helping states offset high premiums and out-of-pocket costs. Some experts are skeptical those amounts will be enough, though.

Tax breaks for the rich that drew criticism in the original bill have been stripped out, but it retains other business tax cuts. It also preserves the original bill’s deep cuts to the rate of growth of Medicaid spending, rolling back the ACA’s Medicaid expansion over the next seven years.

As the title suggests, Republicans aim to pass the bill through reconciliation, a process that enables them to evade a Democratic filibuster if they can secure a simple majority. With 52 Republicans in the Senate, plus the vice president as a potential tiebreaker, the GOP can only afford to lose two votes and still pass the legislation.

Sen. Rand Paul, R-Ky., and Sen. Susan Collins, R-Maine, have already come out strongly against the new BCRA, saying they will not even support the planned procedural vote to bring it to the floor for debate next week. That leaves McConnell with a handful of wavering senators to convince, no margin for error, and parliamentary rules restricting his options.

It also puts them up against an inescapable deadline. O’Connell noted that the Senate can only pass one reconciliation bill per budget year, and Republicans will almost certainly need to devote one to tax reform next year. If they cannot pass a health care bill before the end of this fiscal year, then, they could lose the opportunity.

Of the lawmakers who were on the fence, Sen. Jeff Flake has indicated he may now be on board, and Sen. Lisa Murkowski, R-Alaska, has already secured carve-outs that would send hundreds of millions of dollars to her state. Cruz is working to secure Sen. Mike Lee, R-Utah, who supported a previous version of his amendment but wavered when the final text was released.

Portman, Capito, and Sen. Dean Heller, R-Nev., continue to signal concerns about Medicaid funding. The three senators, plus Murkowksi, had a long meeting with McConnell and Medicaid administrator Seema Varma Thursday, but none came out converted.

Health care policy experts see little in the new legislation that should allay concerns senators had about the original version.

Last-minute concessions required to pass the ACA became highly controversial back in 2010, and Majority Whip John Cornyn, R-Texas, has claimed McConnell will not make state-specific deals. At least one provision in the updated BCRA increasing funding to states with premiums 75 percent higher than the national average does appear tailored to apply to Alaska, though.

According to Leibenluft, any Band-Aids that can be patched on the bill to appease moderates, like further delays in ending the Medicaid expansion or adjusting caps on Medicaid benefits, would do very little to change its impact. The $200 billion McConnell has to play with cannot undo the effects of far larger cuts in funding.

“We could see some of those piecemeal changes,” he said, “but those changes would really be little more than lipstick on a pig at this point.”

“[McConnell] is very good at this, but he has frighteningly little wiggle room,” said Richard Arenberg, a former senior Capitol Hill staffer and co-author of “Defending the Filibuster: Soul of the Senate.”

According to O’Connell, the holdouts are less likely to be swayed by any new sweeteners McConnell throws in than they are to recognize that they simply have a binary decision between this bill and breaking their vows to voters to repeal the ACA.

“These folks have got to now realize this is the choice that you have, and in politics sometimes you have to play the cards that are dealt,” he said.

President Donald Trump, who has not been nearly as hands-on with this bill as President Obama was with the ACA, is now making that case on Twitter as well.

“After all of these years of suffering thru ObamaCare, Republican Senators must come through as they have promised!” he wrote in one of several tweets aimed at Senate Republicans Friday.

Trump’s opinion may not matter to senators directly, but it does energize his very vocal and very passionate base who will demand that the Senate get something across the finish line.

“It’s meant to literally light a fire under their backside,” O’Connell said.

While siding against the bill would surely rile Trump and generate any number of early morning angry tweets, it is less clear that the decision would present a political liability in a reelection campaign. Even among Republicans, the Senate bill has never been very popular.

On Friday, the Kaiser Family Foundation released its July tracking poll, conducted July 5-10, which showed only 28 percent of Americans have a favorable opinion of the bill, and 44 percent have a “very unfavorable” view. It does have support of 60 percent of Republicans, but only about a quarter say they have “very favorable” opinions.

As the GOP forges ahead with its unilateral approach to repealing and replacing the ACA, seven in ten Americans say they would prefer if Republican worked with Democrats to fix the system without repealing it. Trump supporters are pretty much evenly split on which strategy they favor, and about 54 percent of Republicans want their party to continue fighting for their repeal plan.

Arenberg, now a visiting professor at Brown University, observed that Collins wisely avoided being seen as the swing vote by coming out against the bill immediately, but that put even more pressure on the remaining undecideds.

“Dean Heller has made the classic mistake of leaving himself as the likely deciding vote,” he said. “His political circumstance is diabolically difficult.”

Nevada’s Republican governor has criticized the bill’s Medicaid cuts, and if he comes out against it, the less popular Heller will have to decide which side he is on. He is also the only vulnerable Republican up for reelection in 2018 in a state that Hillary Clinton won in 2016.

“He needs to avoid a primary from a Trump loyalist, which he will likely get if he votes no,” Arenberg said. Portman and Capito face a similar quandary, but they have a few more years until they have to defend their vote in a re-election campaign.

O’Connell pointed out that polls have also consistently shown that voters do not want the ACA left as it is either. It is natural for people to fear change, he added, and Republicans have not yet devoted much effort to selling the bill to the public.

If this effort fails in the weeks ahead, Republicans may have to attempt to negotiate with Democrats, but that could prove to be a messy and lengthy process with no guarantee of success. Meanwhile, the uncertainty in the insurance market would drive premiums, deductibles, and Medicaid costs even higher.

“I don’t think it’s dawned on them that not doing anything is not really an option,” he said.

Lawmakers are anxiously awaiting an assessment of the bill by the Congressional Budget Office. The nonpartisan agency estimated that 22 million fewer people would be insured in 2026 under the original version of the BCRA than under current law, many of them because they could no longer afford premiums.

The Trump administration has disputed the accuracy of the CBO, but its conclusions still carry weight on Capitol Hill. It may carry much less weight with voters, though, if they even know what it is. Kaiser found that only 35 percent of Americans had heard or read about the CBO’s report on the original bill, and even fewer were familiar with the details of it.

That may be somewhat reassuring for Republicans who have tried to brush off the CBO’s conclusions about coverage losses. However, once people heard details about the CBO estimates, more than half said it made them less likely to support the bill.

This may be why Republicans are reportedly considering bypassing a CBO score on Cruz’s amendment and relying instead on an estimate from Trump’s Department of Health and Human Services. Once they do have a score, Leibenluft warned there is “a heavy risk” that the GOP may make additional changes, claim they are improving the bill, and vote before the CBO can verify the effects of the revisions.

Even if Senate Republicans can garner 51 votes to pass their version of the bill, the fight is not over. It will then be sent back to the House, where Speaker Paul Ryan will again face the challenge of wrangling the House Freedom Caucus and moderates whom he could barely bring together to pass the original House bill in May.

“I think that all of them are willing to take a vote because they recognize the stakes,” O’Connell said.

That depends on how much McConnell has to give away to get the votes.

“He cannot go so far that Cruz and Lee become a factor again,” Arenberg said. “Even if it squeaks by them, the Freedom Caucus in the House won't take too much more.”

Unless Republicans want to face a scorned and aggrieved base in the midterms, O’Connell said this may be their last chance to live up to their campaign promises.

“If they don’t pull this off, eventually the clock is going to run out on the on September 30,” he said.